Broadband access to the Internet has greatly increased the demand for digital video cameras designed for use with a personal computer (PC). These video cameras, which are also known as Webcams, are connected to a PC and used to produce compressed streaming video data for transmission over the Internet, local area, and/or wide area networks. While early cameras of this type were only capable of producing black and white images, the development of low cost transistor-based, i.e., complementary metal oxide semiconductor (CMOS), imaging sensors has enabled reasonably good color images to be produced by PC cameras, although typically at less than full motion frame rates (i.e., less than 30 frames/second). However, to minimize costs, such cameras have relatively few automated controls. For example, they do not include automatic focusing systems like those normally provided on analog or digital video cameras intended for general purpose use in recording images on magnetic tape. On PC cameras, the lens is typically manually adjustable.
Several factors cause the manual focusing of a PC camera to be very frustrating. Unlike more expensive analog or digital cameras for recording images on tape, PC cameras typically do not include a viewfinder. If a viewfinder is provided, the image seen through the viewfinder is not indicative of the lens focus. Instead, the image produced by a camera must be viewed on a PC monitor. Focusing of the lens is normally done in a preview mode. Since the image in preview mode is usually compressed, details that enable the sharpest focus to be visually determined will be less evident than in an uncompressed image. Also, there is inherently a time delay between the point at which an image signal is supplied by a PC camera and the time at which the image is displayed on a monitor. The delay hinders the manual focusing process. A user manually adjusting the focus on a PC camera while viewing the preview image produced by the camera on the monitor may believe that the camera is properly focused, only to watch the image become less sharply focused. The user will have adjusted the focus control past the point of sharpest focus. The time delay between an adjustment and the corresponding effect on the sharpness of the previewed image during the manual focusing process thus makes it difficult to adjust the camera to achieve the sharpest possible image.
Several other factors contribute to the difficulty in focusing a PC camera. Typically, the size of the preview image being viewed on a computer monitor while adjusting the focus is so small that details of the image that might assist in focusing the camera are not evident. Ambient lighting conditions can also adversely impact the user's ability to properly focus a camera. For example, a poorly lighted scene will result in an image with little contrast, causing the sharpness of the focus to be difficult to visually determine. Sunlight or other lighting conditions that cause glare on the computer monitor on which the preview image is being viewed can also interfere with the focus adjustment.
Accordingly, it will be apparent that providing a less subjective indication of focus sharpness would greatly assist a user in manually focusing a PC camera. Although conventional through-the-lens focusing systems and automated focusing features might be provided on a PC camera, the components required for these solutions to the problem are too expensive to implement at the desired price levels of PC cameras. There is thus a clear need for a lower cost solution to this problem.